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Physical Chemistry: Gas-phase ionic systems, specifically, ion-molecule reactions, chemical bonding within ions and structures of ions.
The primary focus of our research is the study of gas-phase ionic systems, specifically, ion-molecule reactions, chemical bonding within ions and structures of ions. Of particularly interested is the elucidation of systems containing an odd number of electrons involving bonding at calcogens and halogens. The techniques used are high-pressure chemical ionization reactions and Mass Spectrometry/Mass Spectrometry (MS/MS). Ion-molecule reactions and equilibrium experiments are carried out in a highly modified DuPont mass spectrometer while ion-molecule structures and fragmentation reactions (metastable and collision induced dissociation experiments) are studied with a modified VG ZAB mass spectrometer.
An objective is the study of gas-phase ion-molecule reactions forming reactive intermediates or stable product ions containing two-center three-electron bonds (2c-3e bonds). These bonds involve two electrons occupying a s orbital and one electron occupying a s* orbital both of which are localized between two atoms. Thus, these bonds have a bond order of one half. In particular we study 2c-3e interactions between the calcogens and halogens, of the form - X\X, X\X’, X\Y, Y\Y and Y\ Y’ where X represents a calcogen and Y a halogen and the three dots represent the localized three electrons. The Figure shows a collision induced dissociation spectrum of [(CH3)2Te\Te(CH3)2]+ and is described in the legend. Experiments that probe the thermochemistry, the atomic connectivity and structure, and fragmentation dynamics are carried out. The goals of these studies are to better understand the chemistry and structure from a fundamental standpoint.
We also have a keen interest in electrochemical / electrospray mass spectrometry. We, as well as several other research groups, have reported successful coupling of electrochemical methods with electrospray mass spectrometry (EC/ES/MS). This combination has proven to be effective for investigating electrochemical processes; the overriding strength of the method is that it promises the full characterization of the details of electrochemical reactions as well as the study of novel ions. Of particular interest are studies of multiply charged anions. In the gas-phase, multiply charged anions can be very difficulty to make because they can have negative electron affinities (EAs). For instance, C60n-, has negative electron affinities for n greater than one. However, since negatively charged C60 anions are readily generated electrochemically, we were able to detect these ions for n = 3 and 4. Continued studies of other multiply charged fullerides are of interest.
The CID spectra of [(CH3)2Te\Te(CH3)2]+. The largest peak at m/z 160 (CH3)2Te ·+ arises from the cleavage of the Te\Te bond while the small peak at m/z 260 Te2·+ strongly supports the suggested TeTe bonding.
Guo, T.; Li, L.; Cammarata, V.; Illies, A. “Electrochemical/Electrospray/Mass Spectrometric Studies of I- and SCN- at Gold and Platinum Electrodes: Direct Detection of (SCN)3-” Journal of Physical Chemistry B 2005, 109, 7821–7825.
Cammarata, V.; Guo, T.; Illies, A.; Li, L.; Shevlin. P. “Gas-Phase Observation of Multiply Charged C60 Anions” Journal of Physical Chemistry A. 2005 109(12), 2765-2767. (Authors appear in alphabetical order)
King, K. E.; Illies, A.J. “Two-Center Three-Electron Bonds Involving Tellurium” Journal of Physical Chemistry A 2004 108, 2004, 3581
King, J. E.; Illies, A.J. “Two-Center Three-Electron Bonds Involving Selenium” International Journal of Mass Spectrometry 2003 228, 429-437.
King, J. E.; and Illies, A. J. “An Experimental Investigation of Gas Phase Ions of the Form [c-CnH2NS\CH3]+ where n = 2, 3, 4 and 5. Metastable and Collision-Induced Dissociation Results “ Journal of Physical chemistry Part A 2002 106, 12248-12251.